1. Field of the Invention
The invention relates to the field of dairy technique. It has for its object a method of resuspending flocculated milk casein for the obtention of a protein-enriched dairy raw material. Such a raw material may find applications especially for cheese production, but also for obtaining products for alimentary or dietetic use, such as milk powders enriched in proteic substances. The field wherein the invention finds a particularly advantageous application is that of cheese-making.
2. Description of the Prior Art
Casein is the main protein in milk. Being sensitive to acidity and to rennet, it represents almost the 4/5ths of the proteic matters in milk. The other proteic substances, called "whey proteins" or "seric proteins", which are insensitive to the action of rennet while sensitive to that of heat, represent somewhat more than the remaining 1/5th.
The methods used for separating the milk proteins have been improved in the course of time with a view to recover them in an ever increasing proportion and in the least possible denatured state. To the rudimentary, while economical, method consisting of industrial casein preparation there was added the so-called co-precipitation technique. Among the more recent treatments for milk, ultrafiltration was proposed to provide a retentate suitable as a pre-cheese, i.e. a raw material with a composition quite similar to that of drained cheese. Such a retentate contains all the proteins of the original milk in a non denatured state, said proteins having undergone no flocculation. Ultra-filtration, apart from the cyclic character of its operation, does not allow full control of the retentate composition, due to its non-instantaneous nature which permits the evolution of the product subjected to filtration. Form the technological standpoint, recovery of the whey proteins in the soluble state while desirable for some uses, might prove unsuitable for cheese-making, for example, where those proteins bring in fluidity instead of firmness. From the technological standpoint, ultrafiltration is a gentle, but costly technique. Pratically, care should be had of using membranes of sufficiently warranted strength, life-time and aptness to be cleaned without being damaged. In the present state of the art, ultrafiltration of milk for cheese-making, is quite valuable from the theoretical standpoint but liable to raise practical difficulties.
Among the known methods mention may also be made of the so-called CENTRI-WHEY method developed by the firm ALFA-LAVAL, which consists in flocculating the whey proteins in the absence of casein, i.e. in the whey itself, and after their separation by centrifuging, in incorporating said flocculated proteins in the milk for the following cheese-making steps. The whey proteins are coagulated by heating and are present under the form of a suspension sufficiently stable not to settle during renneting. The method thus leads to a milk proteic concentrate wherein the casein is in the form of a colloidal dispersion, and which contains the whey proteins in the flocculated state. From the dietetic standpoint, nutritionists are of opinion that it is not objectionable, to consume whey proteins in the coagulated state instead of the soluble state. While valuable both from the dietetic and economical standpoint, the CENTRI-WHEY method does not lead to a dairy raw material constituting a genuine pre-cheese. The protein milk resulting from the whey protein flocculating step is incorporated in the process milk, this causing a further syneresis, whereby carring out of the method may be continued.